Oil burner control



March 7, 1939. f R. E. FowLER 2,149,842

OIL BURNER CONTROL Filed Dec. 12, 1956 LINE 754 V #r1 iatented' Mar. A7., 1939 on. BURNER ooN'rltoL Robert E. Fowler, Birmingham, Mich., assignorfto' General Motors Corporation,'Detroit, Mich., a;

corporation ofv Delaware Application December 12, 193s, serai Nc. 115,512

z claims, (ci. .15a-a) y This invention-relates to control devices and vmore particularly to control devices for liqui or gaseous fuel burners.

.While the embodiment of this invention is illustrated and described as applied toan electrically operated liquid fuel heating system for domestic purposes, it will be understood that this invention may be used inoth'er heating systems.

In the operation of a liquid or a gaseous fuel burner it is necessary to provide a means to prevent continued operation ofthe burner mechanism if it fails to generate heat at any time when the burner motor is on. 'In addition it is necessary to provide a means to ensure that should -the .current supply to the burner motor fail for any reason it will be impossible to start the motor without producing ignition for the fuel. Accordingly, it isl the primary object of this invention to provide a simplified controlmeans adapted to attain the results above mentioned.'

A specific object of this invention is the provisionof a simplified control means' for a liquid or gaseous fuel-burner involving a two way thermostatically operated'switchand 'a relay utilizmg two coils in different circuits and one in.

which the ignition'mea'ns is controlled-by means of a stack thermostat. i

It is also an object of this inventiony to provide a simplified control circuit'` in which control thermostats are underA lower operating voltages than is the control motor.A

Other advantages' and objects` of this invention reside in the combinations and arrangement of parts as will become more-apparent as the description proceeds. Reference is herein mad'e to the drawing forming a portion of this specication, in which the gure vis a schematic showingof one embodiment of my invention.-

In the drawing M' represents a.- control motor adapted to supply the lliquid fuel and air to the burner. The control motor is shown diagrammatically since the specific ,construction thereof forms no part of the present invention. In the embodiment illustrated in the drawing the ignition is of the intermittentlyenergized type,` i. e., one which is not .on at all times during operation of the motor.- The burner motor M .and lead 4' are in parallel with the primary 2 of a transformer T', while the spark gap 8' is across the secondary 5 thereof.

complete the circuit which includes the primary v2'. A switch 9', which may be of the mercury type, is adapted to make andA break the circuit which includes the-transformer primary 2. The

' 55 switch 9' will preferably be located insuch loca- -tlon will Abe on .t'or circuit closed.

Leads 6', 1-' Y.

tion as to ine-actuated by the stackl thermostat as it moves 'under the influence of the heat in the stack. l The motor circuit includes a lead 54', a normally closed switch S' operated by a relay 55', 5

lead-56', warp switch 36', lead 3'.. the hold coil of relay 51', switch 11', leads 58" and 59' and the primary I4' of transformer'T2'. The holding coil of relay 51'-i s of sufficient strength to hold the lswitch 11'v in position but will not close 10 the same. A stack thermostat .16' having contacts 44' and 46' completes the following circuit: Lead6li, contacts 26211', leads 6I', 52", 63', 64', 65', 66', and the secondary 30' of vtransformer T2'. The circuit for operating relay 55' 1'5 comprises the transformer secondary., 30', lead 61'., lead 6 6', contacts Il'and 26' and lead 60'.

When the room thermostat 25'. requires heat the thermostat contacts will be closed by moving l tothe left as viewed in the iigur'e. The' stack 20 temperature will be such that-the stack thermostat switch contacts and switch .9' will be closed.

I Hence the circuit will be completed through the "close coil of" relay 51' and the motor M' will discharge'a mixture of air and fuel into -the '25 furnace.

and the mixture will be ignited. As the stack heats up the stack thermostat contacts will open and break the circuiti and also open the ignition switch 9'. 'I'he motor o will continue to'operate, however,` the hold coil of relay 51'. being sufficient to maintain the mo- This will continue until the room thermostat contact. v26' is .moved to the right to contactterminall'. -The coil of relay 35 will then be energized .to break the motor circuit -at switch S. This' condition will be maintained until the room coolsbelow the proper temperature whereupon the cycle of operation will be repeated. T l 40 The-control means shown in thedrawing comprises means to stop the control=m`otor should the burner fail lto supply heat for any reason.

"For example, should the supply of fuel fail, the

room thermostat would continue -to .call for heat be completed. The contacts 26', 21' of the room thermostat and the cold contacts 44'., 46' `of the stack thermostat would complete the circuit across `the secondary of'the transformer.'12. The heat- .-50 ing element 52 of the warp switch would begin to heat-up.l since the stack would not be heated the contacts M', '.46' would remain closed and element 52' 'would become heated an amount sufficient to cause the bimetallic warp switch 36' 55 Sinceswitch 9' is now closed the igniopen and break the motor circuit. The switch 38 will preferably be of such form as to demand a manual resetting.

The stack thermostat also acts as a safety control upon a current failure. Should the current fail, switch 11' would immediately break the circuit to the motor since relay 51 would be deenerg'ized. Before the motor circuit could be reqstablished the close coil of the relay would have to be again energized and this could only take place by having the stack thermostat switch contacts be in contact and complete the circuit through the close coil. By the time the latter circuit would be reestablished switch 9' would also be actuated by the stack thermostat and would be in closed position to complete the ignition circuit. The time interval will, of course, be sufficient to allow purging of the furnace of any unburned combustible mixture.

In the circuit illustrated it will be noted that the several control thermostats are connected in the low voltage circuit across the secondary of the transformer T2'. This has the advantage that the circuits may be made and broken without sparking and are more sensitive. For these reasons, I prefer the thermostatic controls to operate under a lower voltage than does the burner motor. The burner motor will supply the power for operating some form of air pump and where liquid fuels are used preferably also provide a power means for an injector.

It will be seen that this'invention comprises a simplied control means for automatic liquid or gaseous fuel burners having certain safety features to prevent operation of the burner motor under undesired conditions. The control circuits are suchas not to readily get out of order and are such as to provide continuous service over long periods of time without attention.

It will be understood thatvarious changes and modifications may be made in the circuits shown and described without departing from the spirit of my invention and I do not Wish to limit the patent granted thereon other than as necessitated by the prior art.

I claim:

1. In a burner control; a power circuit which includes the primary of a transformer; a first relay; a second relay having a hold coil and a close coil; a burner motor and a circuit therefor connected in parallel with the transformer primary when the burner is in operation including a normally closed switch adapted to be opened by the rst relay, a bimetallic switch and a third switch adapted to be moved into closing position by the close coil of the second relay and held in closing position by the hold coil thereof, said hold coil forming a portion of said motor circuit and being connected in series therewith; an ignition means which includes a transformer connected in parallel with the motor; a circuit for said rst relay which includes the secondary of said rst mentioned transformer and a thermostatically controlled switch moved to closing position when a desired room temperature has been attained; a second circuit which includes the secondary of said first transformer, a switch operated by thermostatic conditions in the stack,

the close coil of said second relay, a heating coil' in proximity to the bimetallic switch and a switch moved to closing position when the room thermostat demands heat, said heating coil causing said bimetallic switch in the motor circuit to open shouldv the stack thermostat not open after the burner motor has been operating for a desired time interval; and a switch actuated by the stack thermostat adapted to make and break the ignition circuit.

2. In a burner .control system; a power circuit which includes the primary of a transformer; a first relay; a second relay having a close coil and a hold coil; a burner motor and circuit in parallel with the primary of the transformer during normal burner operation including a normally closed switch adapted to be opened by the rst relay; a bimetallic switch and a third switch adapted to be closed by the close coil of said second relay and held in closed position by the hold coil of said second relay; a room thermostat having a cold position and a warm position; a stack thermostat; an ignition means including a transformer and circuit in parallel with the burner motor; a switch actuated by the stack thermostat adapted to make and break the ignition circuit; means for completing a circuit across the secondary of said first transformer when the room and stack thermostats call for heat including the close coil of said second relay and a heating coil in proximity to the bimetallic switch in the motor circuit, said heating coil being adapted to heat the bimetallic switch to break the motor burner circuit should the stack thermostat not become heated after a desired time interval g' and means to complete a second circuit across the secondary of said rst transformer when the room thermo stat is in warm position including the coil of said iirst relay, whereby said normally closed switch in the burner motor circuit is opened.

ROBERT E. 

